CN111201594A

CN111201594A - Shallow angle, multi-wavelength, multi-photoreceptor, adjustable sensitivity calibration sensor for semiconductor manufacturing equipment

Info

Publication number: CN111201594A
Application number: CN201880066493.5A
Authority: CN
Inventors: 约翰·巴格特; 比利·伯努瓦; 乔·费拉拉; 布莱恩·特里
Original assignee: Axcelis Technologies Inc
Current assignee: Axcelis Technologies Inc
Priority date: 2017-10-25
Filing date: 2018-10-25
Publication date: 2020-05-26
Anticipated expiration: 2038-10-25
Also published as: KR102642205B1; CN111201594B; TWI800544B; WO2019084260A1; US20190120617A1; KR20200071089A; US10794694B2; JP2021501460A; JP7199432B2; TW201928289A

Abstract

The present invention provides a workpiece alignment system having a light emitting device that directs light beams of multiple wavelengths along a shallow-angle path toward a first side of a workpiece plane in a peripheral area. A light receiving device receives the light beams on a second side opposite to the first side. A rotating device selectively rotates a workpiece support. When the workpiece intersects the path, a controller determines the position of the workpiece based on the amount of light beam received through the workpiece. The sensitivity of the light receiving device is controlled based on the transmittance of the workpiece. The position of the workpiece during rotation is determined based on the rotational position, the amount of light beam received, the transmittance of the workpiece, detection of the workpiece edge, and the controlled sensitivity of the light receiving device.

Description

Shallow angle, multi-wavelength, multi-photoreceptor, adjustable sensitivity calibration sensor for semiconductor manufacturing equipment

Priority file

The present application claims the benefit of U.S. provisional application No. US 62/576,791, entitled "shift ANGLE, MULTI-WAVELENGTH, MULTI-RECEIVER, advanced use table SENSITIVITY ALIGNER SENSOR for electronic device and manual evaluation equivalent", filed on 25/10/2017, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates generally to workpiece processing systems and workpiece processing methods, and more particularly to a system and method for handling and aligning workpieces with varying optical transparency.

Background

In semiconductor processing, several operations may be performed on a single workpiece or semiconductor wafer. In many processing operations, a particular orientation of the workpiece and/or knowledge of the position of the workpiece relative to the workpiece support is required in order to properly process or handle the workpiece. For example, operations such as exchanging workpieces between a transport carrier or magazine and a processing system and transferring workpieces from an atmospheric environment to an evacuated environment of a processing chamber of the processing system through one or more load lock chambers may require a particular orientation or knowledge of the spatial location of the workpieces in order to properly handle and process the workpieces.

The workpiece may be oriented (e.g., aligned with the notch) within an evacuated or atmospheric environment by the photosensor such that the light emitter emits and directs the light beam toward the workpiece while rotating the workpiece relative to the light beam. The change in light received by the light receptor can then be used to determine the position of the defined notch in the workpiece and/or the eccentricity of the workpiece position, depending on the manner in which all or part of the light is received. U.S. patent US 5,740,034 to Hiroaki Saeki discloses a system in which a waveform associated with a received optical signal is used to determine the position of a notch and/or the off-center position of a workpiece.

Disclosure of Invention

The present invention provides a system, apparatus and method for accurately determining the position of workpieces having various transmittances, thereby advantageously overcoming limitations in the prior art, increasing accuracy, and minimizing acquisition costs associated with such systems. More particularly, the present invention provides a system and method for advantageously determining the position of a birefringent workpiece using various polarizing filters. In view of this, the present invention provides a positioning solution that can be used for practically any substrate material and thickness, regardless of the various coatings or properties of the substrate.

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

According to an exemplary aspect of the present invention, a workpiece alignment system is provided. The workpiece alignment system includes, for example, a light emitting device configured to direct a light beam at a plurality of wavelengths along a path toward a first side of a workpiece plane associated with the workpiece. The path is associated, for example, with a peripheral region of the workpiece, wherein the path makes a shallow angle with the plane of the workpiece.

A light receiving device is positioned, for example, along the first path, wherein the light receiving device is configured to receive the light beam on a second side of the workpiece plane, wherein the second side is substantially opposite the first side. A workpiece support is further provided and is configured to selectively support the workpiece along a workpiece plane. In one example, a rotation device is operatively coupled to the workpiece support, wherein the rotation device is configured to selectively rotate the workpiece support about a support axis associated therewith.

For example, a controller is further provided that is configured to determine a position of the workpiece based on an amount of the light beam received by the light receiving device through the workpiece when the workpiece intersects the path. The controller is configured to control the sensitivity of the light receiving device based on, for example, the transmissivity of the workpiece, wherein the controller is further configured to determine the position of the workpiece relative to the support axis when supporting and rotating the workpiece via the workpiece support. Determining the position of the workpiece is based, for example, at least in part on the rotational position of the workpiece support, at least a portion of the light beam received by the light receiving device associated with the rotational position of the workpiece support, the transmissivity of the workpiece, the detection of the edge of the workpiece, and the controlled sensitivity of the light receiving device.

For example, the light emitting device is configured to emit light beams of multiple wavelengths across a predetermined width. As another example, the light emitting device is a laser configured to emit a plurality of wavelengths of light beams.

The position of the workpiece can, for example, comprise a two-dimensional offset of the workpiece center from the support axis along the workpiece plane. As another example, the position of the workpiece includes a rotational position of the workpiece about the axis of the support.

In another example, the rotational position of the workpiece about the support axis is correlated to an edge feature of the workpiece. The controller may, for example, be further configured to determine a position of the workpiece relative to the support axis based on an edge characteristic of the workpiece.

The controller may be configured to determine a waveform, for example, wherein the waveform is defined by at least a portion of the light beam received by the light receiving device at a plurality of rotational positions of the workpiece support. The controller may be further configured to determine a position of the workpiece relative to the support axis based on the waveform. In one example, the controller is further configured to scale the waveform based on a transmittance of the workpiece.

In another example, the controller may be configured to determine the edge of the workpiece by ignoring one or more signals along the width of the light-receiving device. The controller may, for example, be configured to ignore one or more signals other than light hysteresis sensed along the width of the light-receiving device.

In another example, the present invention provides a method of aligning a workpiece. The method comprises, for example: placing a workpiece on a workpiece support; and directing the plurality of wavelengths of the beam along a first path toward a first side of the workpiece, wherein the path makes a shallow angle with the plane of the workpiece. The workpiece is rotated about the support axis and receives a beam of light emitted toward the workpiece at a second side of the workpiece while the workpiece is rotated. In addition, the position of the workpiece relative to the support axis is determined based at least in part on the rotational position of the workpiece about the support axis and the received beam, the detection of the edge of the workpiece, and the controlled beam sensitivity.

The above summary is intended only to briefly summarize certain features of certain embodiments of the present invention, and other embodiments may include additional and/or different functionality than that described above. This summary should not be construed, in particular, as limiting the scope of the application. The solution to the above-mentioned related objects of the invention therefore comprises the features that are described hereinafter and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

Drawings

FIG. 1 illustrates a block diagram of an exemplary workpiece alignment system in accordance with an aspect of the present invention;

FIG. 2 illustrates a plan view of an exemplary workpiece on a workpiece support of an exemplary alignment mechanism;

FIG. 3 illustrates a comparison of sensed position of a workpiece and rotational position of a workpiece support according to another exemplary aspect of the present invention;

FIG. 4 illustrates an exemplary workpiece handling system in conjunction with the workpiece alignment system of FIG. 1;

FIG. 5 illustrates a perspective view of an exemplary workpiece alignment system in accordance with an aspect of the present invention;

FIG. 6 illustrates a side view of an exemplary beam of light passing through a workpiece in accordance with an aspect of the present invention;

FIG. 7 illustrates a plan view of an exemplary workpiece alignment system showing a beam partially passing through an edge of a workpiece in accordance with an aspect of the present invention;

FIG. 8 illustrates a block diagram of an exemplary sensor arrangement in accordance with an aspect of the present invention;

9A-9C illustrate various sensor output signals according to aspects of the present invention;

FIG. 10 illustrates a block diagram of an exemplary method for aligning a workpiece according to another exemplary aspect of the invention.

Detailed Description

In semiconductor processing, several operations may be performed on a single workpiece or semiconductor wafer. In general, each processing operation on a workpiece is typically performed in a particular order, where each operation is required to wait until the previous operation is completed. In many processing operations, a particular orientation of the workpiece and/or knowledge of the position of the workpiece relative to the workpiece support is required in order to properly process or handle the workpiece. For example, operations such as exchanging workpieces between a transport carrier or magazine and a processing system and transferring workpieces from an atmospheric environment to an evacuated environment of a processing chamber of the processing system through one or more load lock chambers may require a particular orientation or knowledge of the spatial location of the workpieces in order to properly handle and process the workpieces.

The workpiece may be oriented (e.g., aligned with the notch) within an evacuated or atmospheric environment by the photosensor such that the light emitter emits and directs the light beam toward the workpiece while rotating the workpiece relative to the light beam. The change in light received by the light receiving device may then be used to determine the position of the notch defined in the workpiece and/or the eccentricity of the workpiece position, depending on the manner in which all or part of the light is received.

Such positioning via the light-sensitive sensor is already sufficient to accurately determine the position of the workpiece, which is opaque to the emitted light, see conventional silicon substrates. However, when substrates or workpieces undergoing processing differ from each other in material (e.g., silicon versus silicon carbide), the use of conventional photosensitive sensors and aligners can result in various positioning errors, particularly where the substrates are partially transparent to the emitted light. For example, differences in transmission across the wafer can cause significant errors in positioning using conventional alignment systems and methods. The transmittance and emissivity may vary from workpiece to workpiece due to the coating or device on a particular workpiece.

Systems for aligning conventional semiconductor wafers have been developed for silicon wafers that rely on the silicon wafer to block the passage of light between the light source and the sensor, wherein the silicon wafer is opaque to light sources of long wavelengths. However, wafers made of silicon carbide (SiC) are not opaque, but transmit light of long wavelengths, and are therefore transparent or translucent to conventional light sources. This transparency can result in difficulty in sensing and aligning silicon carbide wafers using previously designed systems for sensing and aligning silicon wafers. The present invention further appreciates that after various processing steps have been performed on a silicon carbide wafer, the silicon carbide wafer may be densely covered with thin films, devices or metal lines, and thus there may be variations in the degree of transparency, with the potential result being substantial signal fluctuations.

Accordingly, the present invention relates generally to a workpiece handling system for semiconductor processing, and more particularly to an alignment apparatus configured to characterize and/or align workpieces having varying optical transparency.

Accordingly, the present invention is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It is to be understood that the description of these aspects are for purposes of illustration only and are not to be construed in a limiting sense. For purposes of explanation, numerous specific details are set forth below in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. Further, the scope of the present invention should not be limited by the embodiments or examples described below in connection with the accompanying drawings, but should be defined only by the appended claims and equivalents thereof.

It should also be noted that the drawings are intended to illustrate certain aspects of embodiments of the invention and therefore should be considered illustrative only. In particular, the elements shown in the figures are not necessarily to scale relative to each other, the arrangement of elements in the figures being chosen for a clear understanding of the corresponding embodiments, and are not necessarily to be construed as representing actual relative positions of the elements in practice, in accordance with embodiments of the present invention. Furthermore, features of the various embodiments and examples described herein may be combined with each other, unless specifically noted otherwise.

It should also be understood that in the following description, any direct connection or coupling between functional modules, devices, components, circuit elements or other actual components or functional components shown in the figures or described herein may also be implemented through an indirect connection or coupling. Furthermore, it should be appreciated that the functional blocks or units shown in the figures may be implemented in an implementation as individual features or circuits, and may also or alternatively be implemented in whole or in part in another implementation as common features or circuits. For example, several of the functional blocks may be implemented in software running on a common processor (e.g., a signal processor). It should also be understood that any connection described below in the specification based on wires may also be implemented as a form of wireless communication unless specified to the contrary.

In general, the aligner includes a light emitter that directs a light beam toward an edge of the workpiece and a light receiver, and further determines an amount of emitted light that cannot reach the light receiver due to being blocked as the workpiece rotates about the rotation axis. For example, if the center of the workpiece deviates from the rotation axis of the aligner, the workpiece blocks a varying amount of emitted light as the workpiece rotates, and there is a variation in the amount of light received by the light receiver. The amount of blocked light is expressed, for example, as a percentage of the total emitted light. The amount and variation of light received is then converted to a workpiece-related dimension (e.g., offset), which is used by the end effector to retrieve the workpiece at the center of the workpiece in one example.

Referring to the drawings, FIG. 1 illustrates an exemplary workpiece alignment system 100 according to one or more aspects of the present invention. The workpiece alignment system 100, for example, includes a workpiece support 102, the workpiece support 102 configured to selectively support a workpiece 104 along a workpiece plane 106. The workpiece support 102 may include, for example, any number of support mechanisms, such as pins, plates, or other mechanisms (not shown) operable to selectively support the workpiece 104.

According to an exemplary aspect, a light emitting device 108 is positioned on one of the first side 110 and the second side 112 of the workpiece plane 106, wherein the light emitting device is configured to direct a light beam 114 along a path 116. The path 116 is associated with, for example, a perimeter 118 (e.g., a perimeter region or edge) of the workpiece 104.

The rotation device 120 is further operatively coupled to the workpiece support 102, wherein the rotation device is configured to selectively rotate the workpiece support about a support axis 124 (e.g., as indicated by arrow 122). The support axis 124 is, for example, perpendicular to the workpiece plane 106.

In a particular example, the light emitting device 108 (e.g., also referred to as an emitter) is configured to emit light at multiple wavelengths. The light emitted by the light-emitting device 108 at one or more of these multiple wavelengths may be determined, for example, based on the composition of the workpiece 104. A light receiving device 126 (also referred to as a receptor, for example) is further provided, and the light receiving device 126 is configured to receive the light beam 114 while the workpiece support 102 rotates about the support axis 124.

According to several aspects of the invention, the workpiece alignment system 100 further includes a controller 128, wherein the controller is configured to determine one or more of a position and an orientation of the workpiece 104 relative to the workpiece support 102 based on an initial transmissivity 130 (e.g., an amount of transmission) of the beam 114 and a receive signal 132 associated with the beam received by the light receiving device 126 (e.g., passing through and/or across the workpiece). For example, the received signal 132 of the beam 114 is based at least in part on the material composition of the workpiece 104, one or more layers (not shown) formed on the workpiece, one or more devices (not shown) formed on the workpiece, and one or more operations previously performed on the workpiece, such as a previous ion implantation or other semiconductor processes previously performed on the workpiece.

As another example, the controller 128 is further configured to determine a position 134 of the workpiece 104 relative to the support axis 124. It should be noted that the controller 128 may comprise, for example, a plurality of individual controllers (not shown) associated with various components of the processing system, or may be a single controller for the entire system, and all such controllers are contemplated as falling within the scope of the present invention.

The position 134 of the workpiece 104 may be determined, for example, by the controller 128, such that the controller is configured to determine the position of the center 136 of the workpiece 104 relative to the support axis 124 of the workpiece support 102, as seen in fig. 2. For example, as shown in FIG. 1, determining the position 134 of the workpiece 104 relative to the support axis 124 is based at least in part on the rotational position 138 of the workpiece support 102 and the received signal 132, which is indicative of a portion 140 of the light beam 114 received by the light receiving device 126.

A portion 140 of the light beam 114 received by the light-receiving device 126 is associated with, for example, the rotational position 138 of the workpiece support 102. In one example, the position 134 of the workpiece 104 determined by the controller 128 includes a two-dimensional offset of a center 136 of the workpiece from the support axis 124 along the workpiece plane 106, as seen in FIG. 2. The position 134 of the workpiece 104 may further include a rotational position 138 of the workpiece 104 or the workpiece support 102 about the support axis 124, wherein the rotational position of the workpiece about the support axis is associated with an edge feature 142 of the workpiece, and wherein the controller 128 of fig. 1 is further configured to determine the position of the workpiece relative to the support axis based on the edge feature of the workpiece. The edge feature 142 in fig. 2 may include, for example, a notch, flat, or other feature associated with the perimeter 118 of the workpiece 104.

Fig. 3, for example, illustrates a plot 160 of rotational position 162 (e.g., provided by a servo motor or other device associated with the rotation apparatus 120 of fig. 1) versus output 164 from the light-receiving device 126 of fig. 1, where the center 136 of the workpiece 104 can be inferred from an output signal curve 166 (from the received signal 132), which output signal curve 166 indicates that the edge feature 142 passed through the beam 114 (e.g., shown in fig. 3 at position 168), and the size of the edge feature is known.

Accordingly, the controller 128 in fig. 1 can determine an offset vector value associated with the center 136 of the workpiece 104, which can be provided to the robotic arm 170 shown in the workpiece handling system 172 of fig. 4. The robotic arm 170, for example, may be configured to pick the workpiece 104 from the workpiece support 102 based on the offset vector value, and when the workpiece is picked from the workpiece alignment system 100 in fig. 1, the workpiece is substantially centered with respect to the support members 174. The rotational position of the workpiece 104 can further be used to rotationally align the workpiece relative to the workpiece alignment system 100 before the workpiece is picked up by the robot arm 170 and transferred to one or more workstations 176, such as a processing chamber, load lock chamber, transfer system, or other equipment for processing the workpiece.

Silicon carbide (SiC) wafers used in semiconductor processing are translucent and conventional alignment sensors (e.g., 10mm sensors from ohrong) can produce inconsistent results, leading to wafer handling errors and aligner failures. These problems are particularly pronounced when the device wafer and the wafer are more transparent. Because SiC is translucent, 650nm light from conventional sensors can pass through the block of material, providing inconsistent results for conventional light receptors. Such failures occur increasingly frequently when devices are formed or otherwise present on the wafer, because the devices block a portion of the light, while the portion of the wafer without devices allows light to pass through. This will produce large fluctuations in the readback signal, making it difficult for the fitted curve and algorithm to find the center and orientation of the wafer using a conventional calibrator.

The present invention utilizes a calibration sensor configured to generate a broad beam of light at multiple wavelengths in conjunction with an edge detection scheme, wherein the sensitivity of the calibration sensor is further tunable. The calibration sensor is further oriented at a substantially shallow angle to the workpiece so that the calibration sensor of the present invention will improve the stability of the readback signal.

Accordingly, the present invention provides a multi-wavelength edge detection sensor with tunable sensitivity to workpieces comprising transparent or translucent materials. The sensor is mounted at a shallow angle to the workpiece to increase the length of the intersection. The light-emitting device 108 of fig. 1, for example, is configured to emit light at multiple wavelengths (e.g., a multi-wavelength laser), such that multiple wavelengths may improve the issues associated with material uniformity of the workpiece 104 that is opaque or transparent to a single wavelength of light. Accordingly, the light receiving device 126 (e.g., one or more light receptors) is configured to receive light at multiple wavelengths to determine the distance from the edge of the light emitting device 108 to the edge or perimeter 118 of the workpiece 104 and to disregard any light that passes through the workpiece and is received by the light receiving device.

Thus, the present invention provides a stable read-back even if the transparency varies across the workpiece 104. The edge of a transparent object, such as the workpiece 104, may be less transmissive than most or the rest of the object. The sensitivity of the light-receiving device may thus be adjusted or otherwise controlled to identify the edge or perimeter 118 of the workpiece 104 and ignore most or the remaining interior portions, resulting in a more stable signal associated with edge detection. In addition, by positioning the light receiving device 126 (e.g., a sensor) at a shallow angle to the workpiece 104, the light 114 (e.g., laser light) is transmitted through a longer length of the workpiece or a cross-section of the workpiece, resulting in a smaller amount of light being transmitted to the light receiving device 126. Thus, the difference in signal strength is advantageously increased between the case where the light 114 passes through a quasi-transparent portion of the workpiece and the case where the light 114 and the workpiece do not intersect each other, thereby providing a more accurate and repeatable mechanism for identifying the position of the workpiece.

Accordingly, the present invention provides a multi-wavelength, multi-photoreceiver, adjustable sensitivity alignment apparatus 200, such as that shown in FIG. 5, in which the light emitting device 108 and the photoreceiver device 126 are mounted at a shallow angle 202 to the workpiece 104 (also known as a wafer). Accordingly, due to the shallow angle 202, as shown in FIG. 6, a greater thickness of the workpiece 104 is allowed to block light 114, such that the readback signal is both smooth and consistent. The light emitting device 108 and the light receiving device 126 of the aiming device 200 emit and receive, respectively, light 114 at, for example, multiple wavelengths. For example, various materials are transparent to light 114 of different wavelengths based on the material properties. By using multiple wavelengths, the likelihood that a particular material will be completely transparent to a single wavelength can be reduced by aligning the remaining wavelengths of light 114 emitted and received by the apparatus 200. For example, using multiple wavelengths to determine the manner in which light 114 is received for different wavelengths.

Accordingly, light of multiple wavelengths is emitted and received by the light emitting device 108 and the light receiving device 126, and changes in light intensity (e.g., the percentage of received light) over the multiple wavelengths are identified. By examining multiple wavelengths and identifying the wavelength at which the intensity value changes, it can be determined whether the material is opaque to a particular wavelength, even if the other intensities remain constant.

In contrast to conventional sensors, in which light traverses the wafer at about 60 to 90 degrees from the workpiece plane, the present invention advantageously provides that the light emitting device 108 and the light receiving device 126 are at a shallow angle 202 from the workpiece plane 106 of the workpiece 104. The shallow angle 202 may be, for example, less than about 30 degrees from the workpiece plane 106. By providing the shallow angle 202 shown in fig. 6 (e.g., the workpiece 104 intersects the workpiece plane 106 at about 5 degrees), the length 204 of the light 114 through the workpiece is much greater than the length of the light perpendicular to the workpiece plane 106. For example, even if the workpiece 104 is 10% to 30% transparent to the light 114 emitted by the light-emitting device 108, increasing the length 204 of light passing through the workpiece advantageously increases the sensitivity of the device 200.

In addition, the edge detection feature can be further utilized in conjunction with the multi-wavelength light 114 and the shallow angle 202 at which the light emitting device 108 and the light receiving device 126 (collectively referred to as the sensor) are positioned. As shown in fig. 7, the edge detection feature identifies a first signal attenuation, e.g., across a predetermined width 206 of the beam 114, and then assumes that any light beyond or downstream (e.g., closer to the center 136 of the workpiece 104) is blocked by the workpiece 104. In addition, even if a portion 208 of the light 114 passes through the block 210 of material of the workpiece 104, the edge detection features of the present invention can be configured to ignore that portion of the light. In this example, the light beam 114 formed by the light emitting device 108 and received by the light receiving device is substantially in the shape of a strip, as seen in fig. 5 to 7.

In one example, the light emitting device 108 and the light receiving device 126 shown in fig. 7 are configured to provide a width 206 of the light beam 114 from an outer extent 210 to an inner extent 212 (e.g., a 28mm distance). The light emitting device 108 is configured, for example, to emit the light beam 114 at an emitted signal 214 (e.g., full signal strength or 100% signal) toward the light receiving device 126, across its width 206 from the outer extent 210 to the inner extent 212. The light receiving device 126 is configured to receive the light beam 114 from the outer extent 210 to the inner extent 212 in predetermined increments (e.g., 1mm increments) such that a receive signal 216 is associated with each predetermined increment.

In this example, the received signal 216 of the beam 114 received by the light receiving device 126 is substantially equal to the first signal 214 (e.g., full signal strength) from the extension 210 to an edge location 218 (e.g., a distance of 0mm to 18 mm) associated with the perimeter 118 of the workpiece 104. When the beam 114 intersects the workpiece 104 from the edge location 218 to the inner extent 212 (e.g., a distance of 18mm to 28mm), the beam 114 passes through the portion 208 of the block 210 of the workpiece 104 to correspondingly reduce the received signal 216 (e.g., the signal intensity is stepped down to 80%, 60%, etc., which correlates to the transmittance of the workpiece 104).

In one example, the light emitting device 108 and the light receiving device 126 have adjustable sensitivities configured to allow adjustment to a desired trigger point. For example, if the receive signal 216 associated with the beam 114 is reduced from 100% of the transmit signal 214 to 50% of the transmit signal at a location 18mm from the extent 210 (e.g., a "step" in the receive signal), then it can be determined that the edge location 218 associated with the edge or perimeter 118 of the workpiece 104 is 18mm from the extent 210. Additionally, such a received signal 216 associated with the edge position 218 can be used to calibrate the apparatus 200 so that any received signal from the edge position to the inner extent 212 (e.g., 18mm to 28mm from the outer extent 210) can be assumed to be blocked or interrupted by the workpiece 104. Thus, even if the beam 114 passes through the block 210 of workpieces 104 and is received at 50% of the transmitted signal 214, it can be assumed that the received signal 216 associated therewith is blocked by the workpiece and ignored.

As another example, as the workpiece 104 rotates, the edge position 218 may change, and thus the received signal 216 may change based on the position of the workpiece on the workpiece support 102 (e.g., the center 136 of the workpiece relative to the support axis 124 of the workpiece support, as shown in fig. 2). As such, the controller 128 of fig. 1 can be configured to determine the edge location 218 of fig. 7 and/or the center 136 of the workpiece 104. Additionally, to detect the edge 118 of the workpiece 104, the light receptor device 126 can include a plurality of light receptors configured to respectively determine the percentage of the light beam 114 received across the plurality of light receptors, thereby determining the edge location 218 by differentiating the received signal 216 along the width 206 of the light beam 114. For example, if the first five of the plurality of light receptors of the light receiving device 126 produce the received signal 216 at 100% of the emitted signal 214, and the sixth light receptor of the plurality of light receptors reduces the percentage of the emitted signal, it can be determined that the edge 118 of the workpiece 104 has been detected at a location associated with the sixth light receptor of the plurality of light receptors, and it can be assumed that any received signal further toward the inward extent 212 is blocked by the workpiece.

Fig. 8 further shows another example in which the sensor device 230 includes the light emitting device 108 and the light receiving device 126. In this example, the light receiving device 126 includes a plurality of sensor cells 232 arranged in an array 234, the array 234 being configured to provide a respective plurality of signals 236. Fig. 9A-9C illustrate examples of multiple signals 236 associated with several workpieces 104 of fig. 8 having various different transmittances, where the multiple signals are observed as one progresses in the direction of arrow 238 (e.g., sensor device 230 is at rest and has multiple sensor units 232A-232 n, spanning 28mm, where n is any positive integer).

Fig. 9A illustrates an example of a plurality of signals 236 of the workpiece 104 of fig. 8, wherein the workpiece is opaque (e.g., light is not transmitted through the workpiece). In this example, the edge 118 of the workpiece 104 is indicated as being at a position 240 halfway between the arrays 234 of sensor cells 232A-232 n, where half of the sensor cells are "ON" (illustrated as unshaded sensor cells) and half of the sensor cells are "OFF (illustrated as shaded sensor cells).

FIG. 9B illustrates an example of a plurality of signals 236 of another workpiece 104 of FIG. 8, wherein the workpiece is composed of a transparent material or materials having different transparencies, such as a silicon carbide (SiC) workpiece having various devices formed thereon. The sensor unit 232B (e.g., unshaded) is, for example, on (e.g., "unblocked" wherein the light 114 is transmitted through the workpiece and received by the sensor unit 232B), while the sensor unit 232A (e.g., "blocked" wherein the workpiece substantially prevents the light from being received by the sensor unit 232A). Thus, the workpiece 104 in FIG. 8, for example, blocks some of the beams 114 while allowing some of the beams to pass through various radial locations. Thus, a varying percentage of the beam 114 is received along the array 234 of sensor units 232A-232 n (e.g., due to devices on the workpiece blocking transmission of light) even though the workpiece 104 may be in a fixed position.

As another example, the sensor output value is a ratio of the total number of sensor cells 232 to the number of cells receiving signals from the light beam 114. For example, in fig. 9A, with twenty sensor units 232A-232 n, ten of the sensor units are blocked while the other ten receive signals. Accordingly, ten divisions by a total of twenty sensor units 232 result in 50% of the total transmit signal 240 received in fig. 8.

In fig. 9B, since some light is transmitted through the workpiece, when proceeding in the direction of arrow 238, signals are received for ten sensor cells 232K to 232T, then sensor cell 232K is blocked, then signals are received in sensor cell 232I, and so on. Even if the workpiece is in the same position, six of the twenty light receptors may be blocked, such as by the device, the film, or a slightly less transparent portion of the workpiece. Fig. 9C shows another example of sensor cells 232A through 232n, shown partially transmitting through the workpiece, with five of the twenty sensor cells being blocked.

The edge detection scheme described above determines that the first sensor cell 232 is blocked when viewed from the same direction as arrow 238, thereby assuming that more sensor cells proceeding later than the blocked cell are also blocked. Even if a portion of the light is transmitted through the workpiece to the outside of the first blocked sensor cells 232, it is automatically assumed that these sensor cells are also blocked. However, the position of the edge 118 may change, for example, as the workpiece 104 in FIG. 1 rotates. But the edge 118 blocks at least some of the light 114.

Thus, the present invention further provides a shallow angle 202 of the sensors (e.g., light emitting device 108 and light receiving device 126), multiple wavelengths of light 114, and a sensor with adjustable sensitivity as shown in FIG. 6 to more accurately determine the edge 118 of the workpiece 104. The first sensor unit 232 in fig. 8 may be blocked by a device formed on the workpiece 104, a transparent material or substrate of the workpiece, or the edge 118. For example, a transparent material may not be 100% transparent, even at the low transmission end, the material may block a small amount of light. But by adjusting the sensitivity of the sensor unit 232, a command can be provided that does not "trigger" or activate the sensor unit if a predetermined amount of light is not received, such as 80% of the emitted light. In this way, even if the material of the workpiece 104 is translucent and 50% of the light passes, the sensitivity can be adjusted to require 80% of the light to activate the sensor cell, which can be considered blocked if 50% of the light is blocked.

Accordingly, the present invention provides a combination of a shallow angle sensor, variable sensitivity and multi-wavelength light to determine the edge of a workpiece.

According to another exemplary aspect, FIG. 10 presents a method 300 of aligning a workpiece. It should be noted that while the exemplary method is illustrated herein as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events, as some steps may, in accordance with the invention, be performed in a different order and/or concurrently with other steps apart from that shown. Furthermore, not all illustrated steps may be required to implement a methodology in accordance with the present invention. It will also be appreciated that the method may be implemented in conjunction with the systems described herein as well as in conjunction with other systems not illustrated herein.

As shown in fig. 10, the method 300 begins with act 302, wherein a workpiece is placed on a workpiece support. In act 304, a beam of one or more wavelengths is directed along a first path toward a first side of a workpiece. The beam is emitted, for example, at a shallow angle to the workpiece so that the amount of light passing through the length of the workpiece is much greater than the amount of light passing through the thickness of the workpiece. In act 306, the beam is directed further toward the periphery of the workpiece and the workpiece is rotated about the support axis. In act 308, the beam is received while the workpiece is rotating. In act 310, the sensitivity of the light beam is controlled or adjusted to provide a desired signal. In act 312, a position of the workpiece relative to the support axis is further determined. Determining the position of the workpiece in act 312 is based at least in part on the rotational position of the workpiece about the support axis and the received light beam, wherein the light beam is apportioned according to the controlled sensor sensitivity and the transmissivity of the workpiece.

Although the present disclosure has been described with respect to a certain preferred embodiment or embodiments, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be suitable or advantageous for any given or particular application.

Claims

1. A workpiece alignment system, comprising:

a workpiece support having a support axis, wherein the workpiece support is configured to selectively support a workpiece along a workpiece plane;

a light emitting device configured to direct a beam of one or more wavelengths toward a first side of the workpiece plane along a path, wherein the beam is a ribbon beam and has a width associated therewith, wherein the path is associated with a perimeter region of the workpiece, and wherein the path is at a shallow angle to the workpiece plane;

a light receiving device positioned along the path and configured to receive a light beam on a second side of the workpiece plane, wherein the second side is opposite the first side, and wherein the light receiving device comprises a plurality of sensor cells configured to receive a respective plurality of portions of the light beam along a beam width, wherein the plurality of sensor cells are configured to define a plurality of receive signals associated with the respective plurality of portions of the light beam; and

a controller configured to determine an edge of the workpiece relative to the support axis based at least in part on a differential of the plurality of received signals when the workpiece intersects the path, and wherein the controller is configured to control the sensitivity of the light receiving device based on the transmittance of the workpiece.

2. The workpiece alignment system of claim 1, further comprising: a rotation device operatively coupled to the workpiece support and configured to selectively rotate the workpiece support about the support axis, wherein the workpiece includes an edge feature associated with an edge of the workpiece, and wherein the controller is further configured to determine a position of the workpiece relative to the support axis based on a rotational position of the workpiece support and a differential of the plurality of received signals when the edge feature intersects the path.

3. The workpiece alignment system of claim 2, wherein the controller is further configured to determine a waveform, wherein the waveform is defined by portions of the light beam received by the light receiving device at a plurality of rotational positions of the workpiece support, and wherein the controller is further configured to determine the position of the workpiece relative to the support axis based on the waveform.

4. The workpiece alignment system of claim 3, wherein the controller is further configured to scale the waveforms based on a transmittance of the workpiece.

5. The workpiece alignment system of claim 1, wherein the shallow angle is about 5 degrees from the workpiece plane.

6. The workpiece alignment system of claim 1, wherein the light emitting device comprises a laser configured to emit a beam of light at one or more wavelengths.

7. The workpiece alignment system of claim 1, wherein the controller is configured to determine a first blocker when the plurality of receive signals are viewed from an outer extent to an inner extent of a beam width, and wherein the controller is configured to selectively ignore receive signals for which any of the plurality of receive signals are defined outside the first blocker.

8. A workpiece alignment system, comprising:

a light emitting device configured to direct a beam of light at one or more wavelengths along a path toward a first side of a workpiece plane associated with a workpiece, wherein the path is associated with a peripheral region of the workpiece, and wherein the path makes a shallow angle with the workpiece plane;

a light receiving device positioned along the path and configured to receive a light beam on a second side of the workpiece plane, wherein the second side is opposite the first side;

a workpiece support configured to selectively support the workpiece along the workpiece plane;

a rotation device operatively coupled to the workpiece support and configured to selectively rotate the workpiece support about a support axis; and

a controller configured to determine a position of the workpiece relative to the support axis based at least in part on an amount of the light beam received by the light receiving device when the workpiece intersects the path as the workpiece is rotated via the workpiece support, and wherein the controller is configured to control a sensitivity of the light receiving device based on a transmittance of the workpiece.

9. The workpiece alignment system of claim 8, wherein the shallow angle is about 5 degrees from the workpiece plane.

10. The workpiece alignment system of claim 8, wherein the light emitting device comprises a laser configured to emit a beam of light at one or more wavelengths.

11. The workpiece alignment system of claim 8, wherein the light emitting device is configured to emit a plurality of wavelengths of light beams across a predetermined width thereof.

12. The workpiece alignment system of claim 8, wherein the position of the workpiece comprises a two-dimensional offset of a center of the workpiece from the support axis along the workpiece plane.

13. The workpiece alignment system of claim 12, wherein the position of the workpiece further comprises a rotational position of the workpiece about the support axis.

14. The workpiece alignment system of claim 13, wherein the workpiece comprises an edge feature, wherein the controller is configured to determine a rotational position of the workpiece relative to the support axis based at least in part on an amount of the light beam received by the light receiving device when the edge feature intersects a path as the workpiece is rotated via the workpiece support.

15. The workpiece alignment system of claim 8, wherein the controller is further configured to determine a waveform, wherein the waveform is defined by at least a portion of the light beam received by the light receiving device at a plurality of rotational positions of the workpiece support, and wherein the controller is further configured to determine the position of the workpiece relative to the support axis based on the waveform.

16. The workpiece alignment system of claim 15, wherein the controller is further configured to scale the waveforms based on a transmittance of the workpiece.

17. The workpiece alignment system of claim 8, wherein the light-receiving device comprises a plurality of sensor cells configured to receive a respective plurality of portions of the light beam along a width of the light beam, wherein the plurality of sensor cells are configured to define a plurality of receive signals associated with the respective plurality of portions of the light beam, and wherein the controller is configured to determine the edge of the workpiece by selectively ignoring one or more of the plurality of receive signals.

18. The workpiece alignment system of claim 17, wherein the controller is configured to determine a first blocker when the plurality of receive signals are viewed from an outer extent to an inner extent of a beam width, and wherein the controller is configured to selectively ignore receive signals for which any of the plurality of receive signals are defined outside the first blocker.

19. A method of aligning a workpiece, the method comprising:

placing the workpiece on a workpiece support;

directing a plurality of wavelengths of a light beam along a first path toward a first side of the workpiece, wherein the path makes a shallow angle with a workpiece plane;

rotating the workpiece about a support axis;

receiving a beam of light emitted toward the workpiece to a second side of the workpiece while the workpiece is rotating; and

determining a position of the workpiece relative to the support axis based at least in part on a rotational position of the workpiece about the support axis and the received light beam, detection of workpiece edges, and controlled beam sensitivity.

20. The method of claim 19, wherein determining the position of the workpiece relative to the support axis comprises determining one or more of a rotational position of the workpiece about the support axis and a two-dimensional offset of a center of the workpiece relative to the support axis.